The thermally-induced misalignment of fiber collimators in laser packaging of optical module under accelerated temperature cycle testing has been studied both experimentally and numerically. Two types of laser welding clips for fiber/fiber collimator,the saddle-shaped and the arch-shaped were employed in the testing. Experimental results showed that the fiber angular misalignment when using saddle-shaped clip is up to 0.023°after undergoing 10 temperature cycles,whereas the misalignment of arch-shaped is 0.01°,about tw two times less than that of the saddle-shaped. A nonlinear thermal-elasticity coupled finiteelement analysis (FEA)has also been utilized to analyze the properties of residual stresses and consequent angular misalignment of collimators. Experimental measurements of the collimator angular misalignment were in a good agreement with the FEA calculated results. The saturated thermally induced angular shift was calculated to be 0.043° for arch-shaped clip in comparison with 0.065° for saddle-shaped clip,and Von Mises stresses were also presented for the both kinds of clips. It was concluded that arch-shaped clip exhibits a 50% higher thermal stability in optical module packaging.